Mississauga Centre RASC

92nd Meeting

                                                                                                Speaker’s Night        

Day:                Friday October 12, 2007

Speaker:         Maria Short

The Challenge of Space Design

Maria Short from the U of T Institute of Aerospace Laboratories spoke about the design of spacecraft and satellites   She began by mentioning the father of human spaceflight, Konstantin Tsiolkovsky, who theorized multistage boosters, space station and airlocks. 

A satellite is a spacecraft launched to orbit the Earth or another body.  Satellites are used to monitor the Earth, for astronomy such as MOST and Hubble, for communications such as Anik, for navigation as the GPS satellites, as a space station, or for military purposes.   A satellite in a low Earth orbit (to 2000 km) goes around the Earth in about 90 minutes at 8 km/sec. while a medium orbit is at 2000 to 35786 km.  A geosynchronous satellite has an orbital period of 24 hours at 35,786 km with a space allocated to each country.  

Radiation, the solar wind and the Sun’s magnetic environment can affect satellites by making a  switch from “on” to “off”, changing false “stars” for navigation and causing  loss of control.  Solar storms can cause atmospheric drag.  Out gassing from a satellite including from sealants, lubricants, adhesives, metals and glass creates a challenge when materials condense on optical elements, radiators and solar cells.  Extreme temperatures with sun or shade affect satellite performance. 

A satellite consists of the power structure often as solar panel(s), communication and propulsion components, computer and the bus or body. The bus encloses the scientific or communication equipment, and must be designed so that it can get to the orbit safely and protect the satellite once in orbit.  Temperature extremes can cause lubricant thickening and damage of electronics if too cold.  Thermal control is necessary to keep the satellite within a large survival temperature range, and a smaller operating range.   Both passive and active methods are used to control the temperature such as blankets, paints, heaters, heat exchangers.  For the large amount of electricity required to run the satellite, solar power, batteries or nuclear power can be used.  The internal computer stores and analyzes data, controls functions and logs all that happens.  Communications must allow controllers to talk to the satellite, upload commands, download data and track the satellite.  A satellite would typically first be launched into a low earth orbit and a propulsion burn could then send it to a higher orbit or transfer it to an escape trajectory. Altitude control using spinning wheels in 3 axes enables stabilization of  the satellite in order to allow it to make precise measurements. The higher the satellite in orbit, the larger its footprint, or area on the Earth that can communicate with it.   

Satellite come in various sizes.  The Hubble Space Telescope weighs 11,000kg and is the size of a bus.  A medium sized satellite like Earth Orbiter 1 is 588kg.  MOST, a misrosatellite weighs 53kg.   Canx-2, a micro satellite weighs 3.5kg and is 34 x 10 x 15 cm in size.  Finally, nano satellites at 1 to 10 kg are on the drawing board.  A number of small satellites can share a single launch vehicle thus allowing a cost of $10,000 per kg.

Maria described the MOST satellite, Canada’s first space telescope.  As a light monitor or photometer it continuously monitors a star for up to 7 weeks.  This requires accurate pointing and a polar orbit.  The mission was motivated by the Sun and its oscillations with a desire to study other stars’ seismology and their oscillations.  The four goals are to probe solar type stars, investigate giant extra-solar planets, study rapidly oscillating magnetic stars and observe Wolf Rayet stars.  MOST observed the star Procyon for 33 days and saw no evidence of oscillations.  Skeptics at first thought that this meant the telescope was not sensitive enough whereas in fact this was a new discovery showing that Procyon did not oscillate.  The star eta Bootis was found to have very precise oscillations.  Light signatures from the close giant planet of HD2094596 was observed.  Wolf Rayet 123 and HR 1217, a magnetic pulsating star were studied.  More than 250 guide stars were observed in all.  MOST is now also called “My Own Space Telescope” with invitations to all Canadians to suggest studies. 

The satellite CanX-2, a 3.5 kg nano satellite is to be launched next month from India and will evaluate components for formation flying.  A staff and student effort, CanX-2 is a cube with 3 axis stabilization and will study GPS radio occultation signals, do materials experiments and atmospheric spectrometry. 

CanX-3, Bright Target Explorer (BRITE) is planned for a summer 2008 launch and will do space astronomy complimentary to MOST.  Four of these are planned,  two for Canada and two for Austria.  They will focus for a few months on the brighter stars of the galaxy. They are 5 kg, 20 cm cubes, smaller than MOST with pre-deployed antennas and booms and 3 cm optical telescopes and 11 mega pixel CCD’s. 

CanX-4, the same size as CanX-3, will demonstrate formation flying in space with sub meter accuracy and position control.  Formation flying can be used for 3D remote sensing in real time, on orbit servicing and docking. 

The Space Flight Laboratories have clean rooms and a thermal room for temperature tests. Nano-sat technologies are developed, Sun sensors, propulsion, computing, and ejection modes studeid.  Two new mission concepts are Lunette and Moment.  Lunette should do high resolution gravity mapping of the Moon’s far side.  Because we can only see the near side from the Earth, we do not have good gravity anomaly measurements from the far side.  Mapping far side mascons is necessary for precision navigation, for making topographic maps, for determining a geologic context for far side formations and to identify drilling sites for ice and minerals.  Moment is to study the remnant magnetic field around Mars. from a highly elliptical orbit coming to within 80 km of the south pole where the interest lies.  The web site is www.utias-sfl.net.      

Observing

William Callahan and Randy Attwood spoke about possible observing with the Toronto Centre at Humber Bay, and about observing at Saddington Park.

Submitted by Chris Malicki, Secretary  Chris Malicki, Secretary                               back to Miss Centre. meeting reports page
Mississauga Centre RASC